Hi @Adrian Eu Kai Chwen ,
Thanks for reaching out.
Glad you are able to resolve your issue.
Your understanding is correct. Whenever you sign in Azure portal using Microsoft Personal Account you by default get connected to the Microsoft Services tenant.
Please refer this https://learn.microsoft.com/en-us/answers/questions/1377925/issue-while-logging-in-to-azure-entra-portal-aadst to understand the issue and its solution.
I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution in case you'd like to "Accept" the answer.